These little things are cheap and pretty useful. I’ve used it for monitoring vehicle bus networks etc, it should show driver pwm no problem.
Yeah, but can't I do it with my current meters which can measure Frequency and Duty Cycle? (Both my orange and green ones in the above pics have those settings.)
-Garry
“do it” - which it do you mean? Anyway the answer is probably no regardless of the question. 
Knowing the frequency or duty cycle doesn’t do you a lot of good when you can’t tell what the voltages during the “on” and “off” portions of the cycle are. You’d use a scope to see a trace which probably looks like 0v with a small spike every little while. The actual LED vF would be what’s going on during the “spike” (the ON portion of the cycle). You’d actually be able to see of that on a scope. Apply your imagination to the images in post #6 here.
Some drivers are able to maintain a smooth output with no PWM, even in low modes (the LDCH LD29 is an example). Those drivers would allow you to get a much more accurate reading with your DMM. Most drivers use PWM which ends up being visible on the output to the LED.
I always thought you need an analogue meter to measure the average voltage of PWM. Or put a capacitor in parallel to use a DMM.
lightme, the thing here is that the average voltage does not matter at all. It is simply not relevant. A very good average voltage and average current could be used to determine average “Power” (wattage), but you won’t learn things like LED Vf or other important info related to efficiency. As alluded to earlier, the LED just won’t light up at 1.5v - you’d get nothing. But the actual average voltage could be even lower, say around 1v or who knows?